1. Field of the Invention
The present invention relates to a device for controlling timing of fuel supply to a gas turbine engine for starting of the same.
2. Description of the Prior Art
In a conventional gas turbine engine, an error in ignition for starting the engine exerts remarkably bad influence upon durability of the engine. This is because the error in ignition results in remaining of unburnt fuel within the engine, which causes incomplete partial combustion of the fuel or appearance of hot spots on the inner wall surface of the combustion chamber in the next ignition stroke, leading to damage by heat of materials constituting the engine.
In recent years, various researches have been conducted on making parts of the gas turbine engine requiring heat resisting capacity of ceramics to improve efficiency of the engine by making the same driven at a high temperature, however, it is necessary to prevent any error in ignition for driving such an engine since the ceramic material is breakable by a heat shock although it can make the engine driven at a high temperature.
For improving ignition performance of a gas turbine engine, it is preferable to increase electric discharge capacity of a spark plug or utilize a glow plug which can continuously give ignition energy. The former case is not suitable for vehicles equipped with many electronic parts since there is generated electrically harmful noise while the latter case is regarded as much more suitable for said vehicles since generation of noise is small.
However, there still remain various problems for starting a gas turbine engine in which the flow plug is used.
In general, when the gas turbine engine is to be started, the glow plug is preheated in the first place and after the surface temperature of the glow plug reaches a set degree, the engine is driven by a starter and fuel is supplied to the same and ignited. The time of application of electricity to the glow plug during which the surface temperature thereof reaches the set degree is called preheating time, which varies with the condition of the initial temperature of the glow plug in inverse proportion thereto. However, it has been difficult to directly detect the surface temperature of the glow plug by a temperature sensor since the glow plug is mounted within a combustion chamber of the engine.
The surface temperature of the glow plug is generally raised upon application of electricity to the same, though, when the engine is driven by the starter in the process of temperature rise, it is lowered under the influence of air compressed by the rotor of a compressor. This is because the heat on the surface of the glow plug is absorbed by heat transfer toward the compressed air, and as the engine speed is increased, a great volume of heat is absorbed since the amount of the compressed air is also increased.
Further, the temperature rise characteristic of the glow plug after starting of the engine is changed when there is difference in the initial temperature of the glow plug upon starting of application of electricity to the same. It is considered because the preheating time from the glow plug varies with the initial temperature thereof upon starting of application of electricity and consequently the amount of electric energy applied to the glow plug varies with the temperature, whereby difference is caused in the extent of influence by the compressed air. Thus, if the engine is started by supplying fuel thereto when the speed of the turbine reaches a predetermined point, ignition performance is influenced by the initial temperature of the flow plug to be instable.